Electric vertical (or short) takeoff and landing (VTOL) aircraft use lift fans (rotors) driven by electric motors to provide lift for vertical flight, such as takeoff, hover, and landing. The same or other rotors may be used to propel the aircraft in forward flight.
Electric aircraft typically operate in outdoor environments. Particularly when operating near the ground, as in during takeoff and landing, debris may strike the operating surfaces of the aircraft, including the lift fans and/or other rotors. In flight, birds and other airborne obstacles may strike the lift fans or other rotors.
In addition to needing to be able to withstand contact with foreign objects, lift fans and other rotors must be able to the withstand the forces associated with flight, such as wind, rain, and applying the forces and moments required to control aircraft position and flight.
Electric aircraft lift fans and propellers are powered by onboard batteries. The weight of the aircraft is a significant factor in determining the operating range and other performance parameters of the aircraft. Composite materials may be used to provide a lightweight aircraft, including lightweight lift fan or other rotors, but such materials may be less able than more durable but heavier materials to withstand contact with foreign objects and other stresses of flight.